Revealing the Faraday Depth Structure of Radio Galaxy NGC 612 with Broad-Band Radio Polarimetric Observations

TL;DR

This study uses broadband radio polarimetric observations of NGC 612 to analyze its Faraday depth structure, revealing that most Faraday rotation occurs in a thin skin around the galaxy with an estimated magnetic field strength of 4.2 microGauss.

Contribution

It provides detailed broadband polarimetric analysis of NGC 612, demonstrating that a single polarisation component explains most observations and suggesting the Faraday rotation occurs mainly in a thin boundary layer.

Findings

Most of the Faraday rotation occurs in a thin skin around the galaxy.

A single polarisation component suffices to model the observed spectrum.

Estimated magnetic field strength is 4.2 microGauss.

Abstract

We present full-polarisation, broadband observations of the radio galaxy NGC 612 (PKS B0131-637) from 1.3 to 3.1 GHz using the Australia Telescope Compact Array. The relatively large angular scale of the radio galaxy makes it a good candidate with which to investigate the polarisation mechanisms responsible for the observed Faraday depth structure. By fitting complex polarisation models to the polarised spectrum of each pixel, we find that a single polarisation component can adequately describe the observed signal for the majority of the radio galaxy. While we cannot definitively rule out internal Faraday rotation, we argue that the bulk of the Faraday rotation is taking place in a thin skin that girts the polarised emission. Using minimum energy estimates, we find an implied total magnetic field strength of 4.2 microG.